The present invention relates to a process for forming a multicolor pattern coating film by spray coating which can form a matted multicolor pattern coating film even in high-speed coating such as coil coating.
In spray-coating a moving coated article, it is coated while reciprocating a spray gun to a large extent in a lateral direction of the moving coated article, so that the coating locus is largely zigzagged. Accordingly, if a moving speed of the moving coated article is accelerated usually to 4 m/minute or more, caused is the problem that a non-coated part is produced on the coated article or a thickness of the coating film is scattered to a large extent.
In forming multicolor patterns on a coated article, scattering in the patterns brought about by scattering in a coating film thickness is notably produced, and therefore it is particularly required to decrease scattering in the coating film thickness. Further, it is considered to elevate a reciprocating speed of a spray gun to prevent producing of a non-coated part and scattering in a coating film thickness. However, if the reciprocating speed is increased, a direct advance of coating material particles discharged from a nozzle is varied to a large extent depending on a size of the coating material particles, so that caused is the problem that disturbance is produced on the patterns.
Disclosed as one mean for solving the problems described above in Japanese Patent Application Laid-Open No. 296357/2000 is a process for forming a multicolor pattern coating film which is uniform and has an excellent decorativeness by spray coating in high-speed coating such as coil coating, wherein two or more spray-coating apparatuses having two or more coating material-discharging nozzles are used, and coating materials having coating colors which are different from each other are discharged from at least two coating material-discharging nozzles of the above respective spray-coating apparatuses to form a plural number of unit plural color spray patterns in which the above coating materials having different coating colors are present in a mixture, whereby spray coating is carried out on a coated article so that the respective unit multicolor patterns constituted by a plural number of the above unit plural color spray patterns are partially superposed on unit multicolor patterns constituted by unit plural color spray patterns adjacent thereto.
The problems described above can be solved by this process, but when a multicolor pattern coating film is a low lustrous matted coating film containing a large amount of an extender pigment such as silica, involved therein are the problems that the multicolor pattern coating film formed is not satisfactory in a color-transfer resistance and a stain resistance against an oil-based ink and that a difference in a weather resistance between the respective colors in the multicolor patterns is large and the multicolor pattern coating film is reduced in appearance with the passage of time to a large extent.
An object of the present invention is to provide a process for forming by spray coating, a matted multicolor pattern coating film which is uniform and has an excellent decorativeness and which is excellent in a color-transfer resistance, a stain resistance against an oil-based ink and a weather resistance.
The present inventors have found that a multiple and multicolor pattern can be formed by using two or more spray-coating apparatuses having two or more coating material-discharging nozzles using matted coating film-forming coating materials prepared by blending a resin system of a hydroxyl group-containing resin and a low nuclidic methylated melamine resin with a reaction mixture of a sulfonic acid compound and an excess amount of an amine compound and by superposing a part of the respective multicolor patterns formed by plural spray patterns on multicolor patterns formed by other plural spray patterns and that the object described above can be achieved, and they have come to complete the present invention.
Thus, the present invention provides a process for forming a shrunk matted multicolor pattern coating film having a 60 degree specular gloss of 10 or less determined according to JIS K5400 7.6 (1990) by spray-coating and baking plural coating materials having different colors on a moving strip coated article, wherein the above plural coating materials are shrunk matted coating film-forming coating materials each comprising:
a resin composition containing
(A) 60 to 95 parts by weight of a hydroxyl group-containing organic resin and
(B) 5 to 40 parts by weight of a low nuclidic methylated melamine resin in such a proportion that the amounts of these both components sum up to 100 parts by weight,
(C) a reaction mixture of 1 mole of a sulfonic acid compound and 1.5 mole or more of at least one amine compound having a boiling point falling in a range of 30 to 250xc2x0 C. and selected from secondary amines and tertiary amines in an amount of 0.1 to 3 parts by weight in terms of an amount reduced to the above sulfonic acid compound per 100 parts by weight of the above resin composition, and
(D) a color pigment; and
in carrying out spray coating,
(i) two or more spray-coating apparatuses having two or more coating material-discharging nozzles are used, and the respective coating material-discharging nozzles are disposed toward a coated article face;
(ii) coating materials having coating colors which are different from each other are discharged from at least two coating material-discharging nozzles of the above respective spray-coating apparatuses to form a plural number of unit plural color spray patterns in which the above coating materials having different coating colors are present in a mixture; and
(iii) thus, the respective unit multicolor patterns constituted by a plural number of the above unit plural color spray patterns are partially superposed on unit multicolor patterns constituted by unit plural color spray patterns adjacent thereto on the coated article to form multiple multicolor patterns covering the whole width of the coated article.
Further, the present invention provides a matted multicolor pattern coating film-forming coated plate obtained by the process for forming a multicolor pattern coating film described above.